Electric fuze



April 7, 1959 J. F. MENKE ET'AL 'ELECTRIC Fuza:

3v Sheets-Sheet 1 VFiled June '28., 1954 W ATTDHNEY Filed June 2a, v1954April?, 1.959 Emma UAL Y 2,880,672

ELECTRIC FUZE s shets-sneet 2 iV 31" EY Q, ATTUHNEY April?, 1959' v .1.F. MENK ETA'. 24,880,572

' v ELECTRIC` FUZE Filed June 28. '19521. 3 Sheets-Sheet 3 271 96 f Y i6@J @Pig O l zal En(` v ATTUHNEY United States Patent O ELECTRIC FUZEJoseph Ferdinand Menke and Ernst Hans Doerpinghaus, Zurich, Switzerland,assignors to Society Brinro Limited, Tangiers, a society of TangiersApplication June 28, 1954, Serial No. 439,832 Claims priority,application Luxembourg June 29, 1953 Claims. (Cl. 102-70.2)

The present invention relates to projectiles, and in particularself-propelling projectiles such as rockets, and it is more especiallybut not exclusively concerned with such projectiles fitted with anelectric fuze, that is to say a fuze the detonator of which is fired byan electric igniting device.

' Itis known to control the arming of the fuzeby means of two deviceswhich are successively brought into play and the first of whichkeepsvthe second one inoperative for a time.l This first device servesto prevent the fuze from being armed before the projectile is launchedand during the handling thereof, in particular during itstransportation. The second device, which serves either to release thearming means proper or to prepare or start the operation thereof, isarranged in such manner that the fuze cannot be armed as long as theprojectile has not travelled agiven distance from its launchingapparatu'sI (which may be constituted by a gun, launching track, etc.),whereby explosion of the projectile inv or on the launching apparatus isimpossible.

According to our invention, the iirst mentioned device is arranged to berendered inoperative by an electric impulse which is automaticallyproduced by contacts the operation of which (in particular the closingof which) is produced by a short initial movement of the projectile,when the projectile has not yet left its launching apparatus. j;

According to another feature of our invention,which isapplicable to thecase where the fuze is an electric o ne supplied with current fromvoltage accumulating 'means carried by the projectile (and preferablyconstitutedby a condenser), said voltage accumulating means is chargedfrom a source carried by the launching apparatus and through the circuitconnection and contact means which serve 'to transmit the electricalimpulse which is to render inoperative the first mentioned device. Inparticular, said circuit connection may be providedrbetween a source ofdirect current which serves to charge the voltage accumulating means anda source of alternating current serving to produce the above mentionedelectrical impulse which renders the first device inoperative.

According to still another feature of our invention, the iirst deviceconsists of an element capable ofl being sheared and constituted forinstance by a wire, a small bar or a rod, this element being sheared bythe explosion of a small primer. Preferred embodiments of our inventionwill be hereinafter described with reference to the accompanyingdrawings given merely by way of example andv in which:

Fig. l'diagrammatically shows the front part of a projectilefitted withan electrical fuze and arranged according to the present invention.II-iig. 2 shows the lay-out of the electrical fuze itself.

Fig. 3 is an axial section on the line IIl-III of Fig. 7, showing theswitch means ofthe electric system of a pro jectileV according to theinvention, the movable portion of' said switch means being in the firstposition. l

u response to the initial movement of projectile 1. i this purpose aPatented Apr. 7, 1959 Figs. 4 and 5 are part axial views with themovable element of the switch means respectively in the locked positionand after it has been iirst released.

Fig. 6 is an axial section of the same switch means, on the line VI-VIof Fig. 7, the movable element of the switch means being in the positioncorresponding to the arming of the fuze.

Fig. 7 is a diagrammatic plan view of the above mentioned switch means.

Fig6. 8 is a sectional view on the line VIII-VIII of Fig.

Our invention will now be more particularly described as applied to aself-propelling missile, such as a rocket, iitted with an electric fuze,that is to say a fuze the detonator of which is red by an electricigniting device.

The projectile 1 itself, as diagrammatically illustrated on Fig. l, isof any suitable construction whatever, with the exception of its fuzeand of the means for charging' and arming this fuze. The fuze includesvoltage accu# mulating means constituted for instance by a condenser 2.In order to charge condenser 2 before the projectile is fired off, weprovide a contact 3 insulated from the envelope of the projectile andwhich may be connected to a source of direct current 4. The chargingcircuit is closed through the conducting envelope of the projectilecooperating with a contact 5.

When the projectile is fired off, condenser 2 must be cut oi fromcontact 3, by means of a switch U which will be hereinafter described indetail, this condenser being then connected to several circuits of thefuze system which are to be fed from said condenser. This switch Uincludes, as diagrammatically shown by Fig. 1, a movable arm 7 pivotedabout axis 6 and cooperating with a contact 8. This switch U cuts ofi,before the projectile is launched, any connection between condenser 2and the circuits of the electric fuze which are to be fed from saidcondenser. Fig. 1 diagrammatically shows this position, where arm 7 isnot in contact with stud 8 which is connected to said circuits. Arm 7has an inertia such that it prevents rotation thereof toward contact 8as long as the acceleration of theprojectile has not reached a valuesuihcient to overcome the inertia of the mass of said arm. Furthermore,before the projectile is launched, the movable arm 7 of the switch iskept, by a first holding device, in the position shown by Fig. 1.According to a particular feature of our invention, said holding deviceconsists of a fusible wire 9 extending between arm 7 add a fixed point10. This wire 9 is inserted in series between contact 3 and condenser 2.

In order to melt wire 9 and thus to render they rst locking deviceinoperative, a current impulse of sutiicient intensity is sent throughthe connection between condenser 2 and source 4. Furthermore, in orderto be able to pass through condenser 2, this impulse is an alternatingcurrent impulse, whereas the condenser is charged, as already known, bymeans of direct current. The alternating current impulse passes throughcontacts which are closed by the initial displacement of the pro jectilewhen it is being ired off. For instance, contact 3 may be cut olf fromthe direct current source 4 by this initial displacement and it may bearranged to pass, for a short time, along another contact (not shown onthe drawings) connected with a source of alternating current or with acondenser charged at a relatively high voltage.

However it seems particularly advantageous to insert, between the directcurrent source 4 and contact 3, the secondary 11 of a transformer theprimary 12 of which is inserted in a circuit fed from an alternatingcurrent source 13. This last mentioned circuit includes a switch 14which is normally open and which is to be closed in For push-rod 15,connected with the movable .arm of switch 14,is arranged to bear againsta portion of the envelope of projectile 1 which is so shaped thatv `mustbe limited to a value such that the fusible wire v9 inserted in thecharging Circuit .does not rneltrThiS een. be obtained by yinserting aresistance. not shown by 'the drawing, in one of the connectionsextending from source 4 tocondenser l2. Such a current limiting resist-.ance may be eonstituted. in the construction of Fig- 1, by thesecondary 1 1 of the tranSfOrrner. It may also be constituted by theinternal resistance of the direct Ycurrent source.

Qnce condenser 2 is charged, the projectile is ready Vto be launched. If the projectile is launched, that is to -say if there` is no misre, theinitial movement of the projectile closes switch 14, whereby anValternating current impulse is supplied through transformer 12, 11 to,the charging circuit connected to the condenser. This impulse meltswire 9, so that on the one hand the means .for holding the movable arm 7of switch U in inoperative 1position is eliminated and on the other handcondenser `2 is ent olf from the eharsing Contact .3-

`I f there is a mistire, switch 1 4, does ynot close and condenser 2then remains connected with the charging contacts 3 and 5. I t can thenbe discharged by means of switch 16 (Fig. l) through resistance 1 7.When this has been done, the projectile can be examined without danger,to lind the reason of the breakdown.

Fig. 2 shows the circuits to be fed from condenser 2 when switch arm 7,after having overcome its inertia vowing to the acceleration of theprojectile,V shifts from `the position shown by this ligure to aposition where it is applied on contact 8. Fig. 2 indicates by a dottedlines connection that arm 7 is coupled With a second switch arm 7aarranged to be applied on a contact 8a when arm 7 is applied againstcontact 8. As a consefquence of this movement (closing of switch 7a,8a), the cathode of a gas tube 18 of the so-called thyratron kind, isheated,y the heating current being supplied from a battery element 19.

Among the circuits to be fed from condenser 2 after switch 7, 8 has beenclosed, there is the charging circuit of a condenser 20 called theignition condenser. This condenser 20 is inserted in a circuit includingalso thyra- .tron 18 and a device for firing the detonator, said devicebeing for instance constituted by an electrically ignited primer 21.

Condenser 2 must also supply a negative bias voltage to the grid 22 ofthyratron 18, whereby said thyratron vcuts off the passage of currentthrough its circuit until the detonator is lired. Explosion of primer 21 is p roduced by the movement of a member 23 or by an auto destructiondevice which causes the. voltage of grid 242 to pass from a negativevalue to a positive value.

Member 23 is for instance inertia operated.

Still another circuit fed from condenser 2 is the charge circuit of acondenser 24 which serves to achieve autodestruetion of the projectile.

Resistances R1 and R2 belong to the charge circuit of ianitins,Condenser .2.0 and serve lfor instance to sive the e. Constant. the..entraine of Condenser 29 veine o bout .25 second (thisindication havingno limitative ehnrneterl- Resistance R2. also acts, together- Withanother resistnnee. R3, as. a. voltage dvider. This resistance. R3, when4 it is-not lshoi-t-circuited by member 23, supplies a negative bias togrid 22, as above mentioned.

The feed circuit of condenser 24 includes the charge resistance R4,which is calculated so that the time constant corresponding to thecharge of condenser 24 is for instance of about 5-6 seconds (thisindication having no limitative character).

In shunt with condenser 24, there is a glow lamp 25 and Va grid resistorR5 in series.

This f uze system works as follows:

As soon as contacts 7, 8 and 7a, 8a are closed, ignition condenser 20starts being charged and it is practically charged after 0.25 secondapproximately, so that after this delay, whichserves to prevent anypossibility of explosion in the gun or the launching apparatus, the fuzeis armed. Then, when member 23 is operated and the negative bias of grid22 is eliminated, the ignition current can pass from condenser 20 toprimer 21 and ignite it. If, on the contrary, the, projectile does notmeet any target and therefore. if member 23 is not actu,- ated,condenser 24, after a delay of vfrom tive or six sec.- onds, is suciently charged to supply glow tube 25 with its glow potential, andtherefore in this caseto supply a positive voltage to the grid 2 2 ofthe thyratron. There- Afore condenser 20 discharges into primer 21 andthe projectile is exploded.

According to a modcation which is not shown by lthe drawing, we furtherincrease protection againstan accidental operation of the fuze byshort-crcuiting theigni.- tion element 2 1 by means of aconductormounted in parallel `with said element and in which thereisinterposed a switch which is opened at the same time Aas switches 7, 8and 7a, 8a. are closed.

In the construction of switch U diasrammaticallyillnstrated by Figs. 1and 2, the mechanical safetyvmeans for .normally ,holding `saidswitch incut-off position consists of a fusible wire 9 which is melted by acurrent impulse.

According to a preferred embodiment of our invention an example of whichis shown by Figs. 3 to. 8 said mechanical safety means is constituted bya locking member capable of beingshearecl and which is actually shearedby the explosion of a` smaller primer produced by an electric currentimpulse fed to said primer.

Advantageously, said primer is mounted similarly vto fusible wire 9,that is to say in the connection serving to charge condenser 2 so thatexplosion of said primer not .only renders said mechanical lockingmember inoperatine, but also cuts off condenser 2v from input contact 3.In the construction of Figs. 3 to 7, the switch includes .an .outercasing o r chamber 26 made of an electrically insu,- lating material. Inthe wall of this casing are .disposed three pairs. Of contacts, to wit,`in one axial plane- (that of Fig. 3.),f two pairs of contacts a, a1 andb, Yb1, located .above one. another, and in another axial Plane (that.of Fia- 6). at: right angles. t0. the. first mentioned. one.. .a thirdpair of contacts c, o1, In en -amber 26 ,there isslidf ably mounted, apiston 27 of substantial weight made of an insulating material, Thispiston 2 7 is provided with two diametral holes 28, 29 locatedrespectively in. tngo different; axialplanes at rightangles'; to eachother. In each of these holesr vthere is, provided a pair of contactballs 3.0.321. and asprins? nrginasnidA ballsawnyzfrgnr each. .other ,Seas lto push. thern` against the .inner-wall of casing 26.

I n the position villustrated by Figs. 3I and 4, piston 2 7 is lockedagainst axial movement by a safetyv wire 33 which, extends across thewall of casing 26 and through a hole A2.7.1191? pieten .2.7, the .innerend of Said wire nroieetins.; into a .recess 34. provided .at the toppart; of .the piston, this wire constituting the. l1Ql/.e. mentionedloplgy inanaeniber@ 'In position Q f. ariston. balls .3 .,31 4and Spring:32, whihextend 'n .tb., upper hole. 2.8 .ofthe piston,v .eonsti.t.nte...a .eenneetion bete/eel.:A .contacts a.. al which are locatedv in thecharging circuit of condenser-2;. For this position of ,the piston..condenser 2.-.ean1tl1eref 2,sso,67a

. fore be charged from the outside, throughfcontact 3. The lockingaction of wire 33 must be sutciently strong to prevent shocks as high as200 g (g--acceleration of gravity) from causing the piston to move fromits position shown by Figs. 3 and 4.

In order to eliminate the locking action exerted by wire 33 on piston27, there is provided at the lower end of casing 26 a small detonator 35containing a small amount of a material capable of exploding under theeffect of a spark, for instance tricinate of lead (trinitroresorcinateof lead). This detonator vis fed with current from a connection 36 whichmay constitute a portion of the connection serving to charge condenser2, andin this vcase is in series with contacts a, a1. j

When the detonator is exploded under the effect of a current impulse,safety wire 33 is sheared off and piston Z7 is projected upwardly fromthe position of Figs. 3 and 4 to that of Fig. 5. The top of the pistonis then applied upon shoulder 37 provided inside'chamber 26. `At the endof this movement, the portion 33a sheared ofi from wire 33 is moved,under the effect of its inertia, away from the aperture 27a of thepiston and passes into recess 34, so that there is no danger of itsbraking the movement of piston 27. The direction of the movement of thepiston from the position of Figs. 3 and 4 to that of Fig. 5 is that ofthe projectile as it is being launched and it is therefore opposed tothat of the movement that would tend to be imparted by the inertiaforces to piston 2,7` inside chamber 26. V

Once the projectile has been launched and when its acceleration hasreached a sutiicient value (for instance 30 g), piston 27 movesrearwardly in its chamber under thev effect of its own inertia andpasses from the position of Fig. 5 to that of Fig. 6. In this lastmentioned position, the balls present in the upper conduit 28 form aconnection between contacts b, b1 and the balls present in the lowerconduit 29 form a connection between contacts c and c1. The groups ofcontacts b, b1 and c, c1 correspond to the elements 6, 8 and 6a, 8a ofFig. 2. The group of contacts a, a1 corresponds to' the contact elements7, 9 of Fig. l.

Advantageously, we provide a recess 38, at least in one of the innerwalls of the chamber along the path of movement of contacts b, b1, c,c1, for instance of contact c1, so as to obtain, by cooperation withcontact balls 31, a locking of piston 27 in the position shown by Fig.6.

In a general manner, while we have, in the above description, disclosedwhat we deem to be practical and efficient embodiments of our invention,it should be well understood that we do not wish to be limited theretoas there might be changes made in the arrangement, disposition and formof the parts without departing from the principle of the presentinvention as comprehended within the scope of the accompanying claims.

What we claim is:

l. In combination, a projectile to be fired off from a launchingapparatus, an electric fuze fitted on said projectile and including fuzearming means, electric voltage accumulating means carried by saidprojectile to feed electric current to said fuze arming means, switchmeans inserted between said fuze arming means and said accumulatingmeans, safety means carried by said projectile 4for holding said switchmeans in cut olf ,position between said accumulating means and said fuzearming means, an electric circuit in said projectile including in seriesa contact carried by the external wall of said projectile, said electricvoltage accumulating means, said switch means in cut off position, saidsafety means and a contact, insulated from the tirst mentioned contact,carried by the external wall of said projectile, a iixed circuit carriedby said launching apparatus including a source of direct current andhaving its terminals located on said two contacts respectively when saidprojectile is in said launching apparatus, whereby direct current isthen fed before launching to said accumulating means through both ofsaid circuits connected together, an electrical impulse responsivedevice carried by saidprojectile and inserted in said first mentionedcircuit to make, when an electrical impulse is passed therethrough, saidsafety means inoperative and thus to cause said switch means to shiftfrom cut off position to connecting position between said voltageaccumulating means and said fuze arming means, a source of alternatingcurrent impulse carried byysaid launching apparatus and cooperatingmeans carried by said projectile and said launching apparatus fortemporarily coupling said last mentioned source with said xed circuit inresponse to the initial launching movement of said projectile withrespect to said launching apparatus. l,

2. In combination, a projectile to be fired off from a launchingapparatus, an electric fuze tted on said projectile and including fuzearming means, electric voltage accumulating means carried by saidprojectile to feed electric current to said fuze arming means, switchmeans inserted between said fuze arming means and said `accumulatingmeans, safety means carried by said projectile for holding said switchmeans in cut olf position between said accumulating means and said fuzearming means, an electric circuit in said projectile including in seriesacontact carried by the external wall of said projectile, said electricvoltage accumulating means, said switch`means in cut off position, saidsafety means and a contact, insulated from the first mentioned contact,carried by thev external wall of said projectile, a fixed circuitcarried by said launching apparatus including a source of direct currentand having its terminalslocated on said two contacts respectively whensaid projectile is in said launch-` ing apparatus, whereby directcurrent is then fed before launching to said accumulating means throughboth of said circuits connected together, an electrical impulseresponsive device carried by said projectile and inserted in said firstmentioned circuit to make, when an electrical impulse is passedtherethrough, said safety means inoperative and thus to cause saidswitch means to shift fromv cut off position to connecting positionbetween said voltage accumulating means `and said fuze arming means, athird circuit, including a source of alternating current impulses,4carried by said launching apparatus, a transformer having its primaryin said third circuit and its secondary in said xed circuit, a normallyopen switch in said third circuit, and cooperating means carried by saidprojectile and said launching apparatus for closing said switch inresponse to the initial launching movement of said projectile withrespect to said launching apparatus.

3. A combination according to claim l further including, in said xedcircuit, a resistance, and switch means forming a short-circuit path fordischarge of said voltage accumulating means through said resistance incase of failure of said projectile to be launched.

4. In combination, a projectile to be fired off from a launchingapparatus, an electric fuze titted on said projectile and including fuzearming means, electric voltage accumulating means carried by saidprojectile to feed electric current to said fuze arming means, switchmeans inserted between said fuze arming means and said accumulatingmeans, said switch means including a tixed part and a movable partsensitive to the action of inertia so as to be urged by the inertiacreated by the launching of said projectile toward the position withrespect to said xed part where it connects said voltage accumulatingmeans with said fuze arming means, safety means carried by saidprojectile for holding said switch part in cut off position where saidaccumulating means and said fuze arming means are out of contact witheach other, an electric circuit in said projectile including in series acontact carried by the external wall of said projectile, said electricvoltage accumulating means, said switch means in cut olf position, saidsafety means and a contact, insulated from the first mentioned contact,carried by the external wall of said projectile, a fixed circuit carriedby said launching apparatus including a source of direct ,cimentandihaving Aits terminals lecatedon said. two con:

o impulse is ypassed therethrough, said safety means inoperative`andlthus to cause said switch movable part to shift under the effecto'f the starting acceleration of the vehicle from its cut olf positionto its connecting position between .Said voltage accumulating means andsaid fuze arming means, a source of alternating current impulse carried,bysaid launching apparatus and cooperating means carried by saidprojectile and said launching apparatus for temporarily coupling saidlast mentioned source `with said finedv circuit in response to theinitial launchingy movementv of said projectile with respect to saidlaunching apparatus.

5. A combination according to. `clairrll 4 in which said Safety meansconsist of a fusible wire mounted in said first rnentioned circuit andnormally holding ysaid switch movable part in cutol position withrespect, to saidswitch tilted part- ,6. A combination accordingto claim4 in `which said safety means include a locking wire normally holdingsaid Switch movable part in cut-off position with respect to said switchfixed part, said wire extending transversely tothe direction ofdisplacement of said movable part with respect to said fixed part so asto be sheared by said displacement, and a charge of explosive insertedin said first circuit and adapted to explode in response to the passageof said current impulse for moving saidmovablepart with respectv tolsaid fixed part..

`7 A combination according to claim 6 in which said xged part is acylinder and said movable part a piston Slitlable in said cylinder.

A8 A combination according to claim 6 in whichsaid flared` part is acylinder and said movable part a piston slidable in said cylinder, saidcombination further inleluding means for locking js'aid. piston/inconnecting position nsaid cylinder..

9. In combination, a projectile, an electric fuze fitted on saidyprojectile and including fuze arming means, electric voltageaccumulating means carried by said projectile to feed electric currentto said fuze arming means, switch means inserted between said fuzearming means and said accumulating means, mechanical safety meanscarried lby said projectile for normally holding said switch means incut off position between said accumulatingV means and vsaid fuze armingmeans, electrical impulse operative means carried by said projectile andconnected with said safety means for making said safety meansinoperative, and means operatively connected with said eectrical impulseoperative means ,for feeding thereto an electrical impulse in responseto the tiring off of said projectile.

l0. In combination, a projectile, an electric fuze fitted on. saidprojectile and. having an electric circuit which comprises a controlswitch, said switch including av fixed part carried by said projectileand a movable part capable of occupying either of two positions withrespect to said fixed part, a locking member normally holding saidmovable part in one of said positions, said member being fixed to eachof said parts in the direction of their rela,- tive movement and beingso dimensioned and made of such material as lto be shearable by arelative displacement of said parts from said lastv mentioned positiontoward the other one under the effect of a given thrust, said two partsfitting in each other so` as to form between them a variable volumechamber, an explosive charge insaidy chamber capable by its explosion tosupply such said thrust, and electric means connected with saidexplosive charge to explode it by an electric impulse.

References Cited in the file of this patent UNITED STATES PATENTS

